Compilare: user.cpp: In function ‘bool cmp(std::string, std::string)’: user.cpp:31:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<=b.size();++i) ^ user.cpp: In function ‘void query(std::string)’: user.cpp:75:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a.size();++i) ^ user.cpp: In function ‘int main()’: user.cpp:135:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<x.size();++j) ^ user.cpp: In function ‘bool cmp(std::string, std::string)’: user.cpp:34:1: warning: control reaches end of non-void function [-Wreturn-type] } ^